1. Field of the Invention
The invention relates to the field of antenna. More specifically, a dual-band antenna has a short portion as a function of an inductance.
2. The Related Art
According to the progress of the communication technology, the key development is the transfer from wired to wireless communication. A plurality of different wireless communication bands may be used by devices such as laptops. Therefore, antennas equipping multi-frequency operation for the laptops are one of the development points.
A conventional dual-band antenna is disclosed in U.S. Pat. No. 6,812,892 filed in 2002 Dec. 26. The dual band antenna has a planar conductive element and a feeder cable electronically connecting to the conductive element. The conductive element includes a first radiating strip, a second radiating strip, a ground portion and a connection strip interconnecting the first and the second radiating strips with the ground portion.
The first radiating strip and the connection strip are configured to function as a first planar inverted-F antenna (PIFA) operating in a higher frequency band. The second radiating strip and the connection strip are configured to function as a second PIFA operating in a lower frequency band. The first and the second radiating strips, the ground portion and the connection strip are all disposed in the same plane.
The connection strip includes a first segment, a third segment, and a second segment interconnecting the first and the third segments, the first segment extending from a joint of the first and the second radiating strips, and the third segment connecting with the ground portion.
Because the third segment of the connection strip is parallel to the second radiating strip, an electromagnetic interference is formed therebetween. The electromagnetic interference between the second radiating strip and the third segment may influence antenna characteristic of the lower frequency band of the dual-band antenna to decrease the efficiency of the lower frequency band of the dual-band antenna.
A conventional multifrequency inverted-F antenna is disclosed in U.S. Pat. No. 6,861,986 filed in 2003 Mar. 20. The multifrequency inverted-F antenna includes a radiating element having opposite first and second ends, a grounding element spaced apart from the radiating element, and an interconnecting element extending between the radiating and grounding elements and including first, second, and third segments.
The first segment is connected to the radiating element at a feeding point between the first and second ends. The second segment is offset from the first segment in a longitudinal direction, and is connected to the grounding element. The third segment interconnects the first and second segments. A feeding line is connected to the interconnecting element.
Furthermore, the radiating element and the third segment are formed an electromagnetic interference therebetween when the multifrequency inverted-F antenna operates in wireless operations. The electromagnetic interference between the radiating element and the third segment may influence antenna characteristic of the multifrequency antenna to decrease the efficiency of the multifrequency antenna.